I may be scorned for this but here goes...
If you are considering a termination then its obviously one of those things that you don't believe is wrong to do (I agree with you) so I would like to think that no one else is going to come in and say its wrong etc. You are entitled to your own beliefs on this.
You are at a point in your lives where you're considering big risks for potentially big rewards - wife's new business venture - these could be difficult times until things get settled.
Also, once baby is born,wife will probably have to take some time out to care for her before returning to work which could make starting a new venture very impractical (given that you haven't said what she's thinking of doing, I'm speculating here) and any work she puts towards it may come undone during the time out she takes. Furthermore, does she want the stress of that while being pregnant?
Also, there will be no maternity pay if she's not employed by someone. Maternity benefit will be available but this is less than company maternity pay (90% of wage) for the first 6 weeks of maternity leave, at least.
I think there's a "way" to get through most things - the question is, what are you prepared to give up to do it. I have friends in the same situation; they are happy with baby but they have had to give up a lot of their creature comforts to stay afloat and haven't been on holiday for 4 years.
On the flip side, if you're happy about the idea if being parents now then you can't ignore those feelings.
Sit down and talk through the pro's and cons, identify what you'll have to sacrifice and how long for. Then chuck all that out of the window and go with your instincts.